The present invention relates to a sewing machine frame made from a synthetic resin in which an arm portion, a tower portion and a bed portion are provided integrally. The present invention also relates to a sewing machine having the sewing machine frame.
In the sewing machine frame, a horizontally extending arm portion supports a reciprocation mechanism for a needle carrying a needle thread, and the tower portion vertically extends from the bed portion for supporting the arm portion in a cantilevered fashion. In the bed portion, a loop taker is supported for trapping a loop of the needle thread carried on the vertically reciprocating needle in order to form a stitch.
In the sewing machine, a smooth stitching operation is required. To this effect, vibration and displacement of a needle tip due to the vertically reciprocating motion of the needle must be reduced or minimized, otherwise a loop seizing beak of the loop taker disposed in the bed portion cannot trap the needle thread loop formed by vertical reciprocation of the sewing needle. Thus, the stitching may be degraded.
In order to avoid this problem, the needle and rotary hook timing must be adequately provided. To this effect, the sewing machine frame must provide high rigidity capable of avoiding deformation or displacement thereof due to reaction force occurring when the needle penetrates a workpice fabric. Therefore, in the conventional sewing machine, a metallic frame having high rigidity is provided in an interior of a sewing machine cover, and a stitch forming mechanism including a needle vertical reciprocating mechanism and the loop taker is attached to the metallic frame.
However, such a conventional arrangement is costly, bulky and heavy. More specifically, the sewing machine frame has a rigid box shape arrangement in order to provide high rigidity. Further, the frame is made from a metal such as a cast iron or aluminum, which in turn increase weight and size. Further, high skill and elaboration is required for assembling the sewing machine because the stitch forming mechanism must be installed into the metallic frame through a small area opening thereof. This increases assembly cost.
Laid open Japanese Patent Application Kokai No.Hei-11-137880 discloses a sewing machine frame made from a synthetic resin to reduce production cost and to provide a light weight frame. As shown in FIG. 16, the frame 300 has an open end arrangement in a U-shape cross-section in which a bed portion 304, a tower portion 303 and an arm portion 302 are provided integrally, and a reinforcing plate 301 is fixed between upper and lower portions at the open end of the bed portion 304.
However, the disclosed sewing machine frame 300 provides a rigidity still lesser than that of the metallic frame. More specifically, as shown in FIG. 16, vertical vibration occurs in the arm portion 302 due to a load exerted along a vertical line containing the needle, the load being caused by the reciprocating motion of the needle during stitching operation. Further, a horizontal swing also occurs at an upper portion of the tower portion 303 during stitching.
Such vibration and swing occur due to the cantilevered support structure of the arm portion 302 with respect to the tower 303. That is, a combination of the arm portion 303, the tower portion 303 and the bed portion 304 provides an arcuate recessed wall 305, and a stress generated by the vertically reciprocating motion of the needle will be concentrated on the wall 305. However, the wall 305 does not have a sufficient rigidity, and therefore, such unwanted vibration and swing occur to lower stitching quality in comparison with the conventional sewing machine provided with the metallic frame.
It is an object of the present invention to overcome the above-described problems and to provide a sewing machine frame having a bed portion, a tower portion and an arm portion those integrally with each other and formed of a synthetic resin, yet having high rigidity, and to provide a sewing machine having such an improved sewing machine frame.
This and other objects of the present invention will be attained by a sewing machine frame for sewing machine having a stitch forming mechanism, the sewing machine frame providing a bed portion, a tower portion upstanding from the bed portion, and an arm portion extending from the tower portion in a cantilevered fashion, the stitch forming mechanism being assembled in the sewing machine frame. The sewing machine frame includes an integral main frame body, a plurality of first couplings, an integral frame cover, and a plurality of second couplings. The integral main frame body is made from a synthetic resin and to which the stitch forming mechanism is assembled. The integral main frame body includes a back panel wall having a first peripheral edge, and a first side wall integrally protruding from the first peripheral edge. The integral main frame body provides an arm section, a tower section and a bed section. The first side wall has a first part defining an inward wall section surroundingly provided by the combination of the arm section, the tower section and the bed section. The plurality of first couplings are provided at the back panel wall and are positioned along the inward wall section. The integral frame cover is made from a synthetic resin and is attached to the main frame body. The integral frame cover includes a front panel wall having a second peripheral edge, and a second side wall integrally protruding from the second peripheral edge. The integral frame cover provides a complementary bed section to form the bed portion with the bed section, a complementary tower section to form the tower portion with the bed section, and a complementary arm section to form the arm portion with the arm section. The second side wall has a second part defining a complementary inward wall at a position corresponding to the inward wall section. The plurality of second couplings are provided at the front panel wall and are positioned along the complementary inward wall at positions corresponding to the plurality of first couplings for fixing the frame cover to the main frame body.
In another aspect of the invention, there is provided a sewing machine frame for a sewing machine, the sewing machine including a vertical reciprocation mechanism for a needle carrying a needle thread, and a loop taker trapping a loop of the needle thread carried on the reciprocating needle to form a stitch. The frame includes an integral frame member, a plurality of first couplings and a plurality of second couplings. The integral frame member is made from a synthetic resin and provides an outer surface defining an external shape and an inner surface providing an internal space. The integral frame provides a bed portion for supporting the loop taker in the internal space, a tower portion upstanding from the bed portion, and an arm portion extending from the tower portion in a cantilevered fashion for supporting the vertical reciprocation mechanism in the supporting the vertical reciprocation mechanism in the internal space. A recessed portion being formed by the combination of the bed portion, the tower portion and the arm portion. The integral frame member includes a main frame body and a frame cover. The main frame body has a bed section, a tower section and arm section those integrally with each other and to which the vertically reciprocation mechanism and the loop taker are attached. The frame cover is attached to the main frame body and has a complementary bed section to form the bed portion with the bed section, a complementary tower section to form the tower portion with the bed section, and a complementary arm section to form the arm portion with the arm section. Those complementary bed section, complementary tower section and complementary arm section are integrally with each other for covering the vertically reciprocation mechanism and the loop taker attached to the main frame body. The plurality of first couplings are disposed at the main frame body at positions adjacent to the recessed portion. The plurality of second couplings are disposed at the frame cover at positions corresponding to the positions of the plurality of first couplings for fixing the frame cover to the main frame body.
In still another aspect of the invention, there is provided a sewing machine frame for a sewing machine, the sewing machine including a vertical reciprocation mechanism for a needle carrying a needle thread, and a loop taker trapping a loop of the needle thread carried on the reciprocating needle to form a stitch. The frame includes an integral frame member made from a synthetic resin and providing an outer surface defining an external shape and an inner surface providing an internal space. The integral frame provides a bed portion for supporting the loop taker in the internal space, a tower portion upstanding from the bed portion, and an arm portion extending from the tower portion in a cantilevered fashion for supporting the vertical reciprocation mechanism in the internal space. The integral frame member includes a main frame body and a frame cover. The main frame body has a bed section, a tower section and arm section those integrally with each other and to which the vertically reciprocation mechanism and the loop taker are attached. The main frame body has a first parting face provided with one of a protrusion and a fitting portion or a combination of the protrusion and the fitting portion. The frame cover has a complementary bed section to form the bed portion with the bed section, a complementary tower section to form the tower portion with the bed section, and a complementary arm section to form the arm portion with the arm section. Those complementary bed section, complementary tower section and complementary arm section are integrally with each other for covering the vertically reciprocation mechanism and the loop taker attached to the main frame body. The frame cover has a second parting face in facing relation to the first parting face. The second parting face is provided with one of a fitting portion and a protrusion or a combination of the fitting portion and the protrusion for engagement with one of the protrusion and the fitting portion of the first parting face, whereby relative lateral displacement between the main frame body and the frame cover is avoidable.
In still another aspect of the invention, there is provided a sewing machine frame for a sewing machine, the sewing machine including a vertical reciprocation mechanism for a needle carrying a needle thread, and a loop taker trapping a loop of the needle thread carried on the reciprocating needle to form a stitch. The frame includes an integral frame member made from a synthetic resin and providing an outer surface defining an external shape and an inner surface providing an internal space. The integral frame provides a bed portion for supporting the loop taker in the internal space, a tower portion upstanding from the bed portion, and an arm portion extending from the tower portion in a cantilevered fashion for supporting the vertical reciprocation mechanism in the internal space. The integral frame member includes a main frame body, and a frame cover. The main frame body has a bed section, a tower section and arm section those integrally with each other and to which the vertically reciprocation mechanism and the loop taker are attached. The main frame body has an upper end portion provided with an upper protrusion, and a lower end portion provided with a lower protrusion. The frame cover is to be attached to the main frame body and has a complementary bed section to form the bed portion with the bed section, a complementary tower section to form the tower portion with the bed section, and a complementary arm section to form the arm portion with the arm section. Those complementary bed section, complementary tower section and complementary arm section are integrally with each other for covering the vertically reciprocation mechanism and the loop taker attached to the main frame body. The upper protrusion and the lower protrusion protrude toward the frame cover when the frame cover is attached to the main frame body, and the frame cover has an upper end portion provided with an upper securing part engagable with the upper protrusion, and a lower end portion provided with a lower securing part engageable with the lower protrusion.
In still another aspect of the invention, there is provided a sewing machine including a stitch forming mechanism and the any one of the above described sewing machine frames.